DESCRIPTION (adapted from the application): The Metabolic Core Laboratory provides tools and expertise for the study of metabolic pathways involved in nutrient utilization. The study of metabolic pathways, and especially of insulin action, involves complex methodology, expensive equipment and specialized knowledge. Consolidation of these tools and techniques in a single laboratory has proven to be an accurate cost-effective means of meeting the needs of many members of the CNRU research base. The core was designed to be complementary to the other core laboratories, since investigators interested in nutrient utilization often combine services available through this core laboratory with services available through the Energy Balance and Mass Spectrometry Cores. For example, measurements of insulin sensitivity are frequently obtained in combination with measurements of body composition, energy expenditure and substrate turnover. The Metabolic Core Laboratory has been well-used by investigators in all 4 research focus areas. Although some CNRU investigators may still be performing some of the measurements offered by this core in their own laboratory, the establishment of shared techniques has gradually reduced redundancies and provided these services in a cost-effective manner. One of the goals of this, and other cores, is to provide services to allow investigators to extend their hypotheses beyond their current level of examination. The services of the Metabolic Core Laboratory have been used by many investigators to extend their research beyond the specific hypotheses proposed in their R01 grants. For example, many investigators who did not previously assess insulin action in their own studies have taken advantage of this core laboratory to obtain these measures using the minimum model technique.